Enhanced surface layers by laser cladding and ion sulfurization processing towards improved wear-resistance and self-lubrication performances

Enhanced surface layers with improved wear-resistance and self-lubrication performances were prepared by means of laser cladding and ion sulfurization processing. The microstructure, element distribution, phase composition, valence states, microhardness and wear resistance of the composited layers were investigated. The results show that Ni-based cladding coating is composed of gamma-(Fe, Ni), Cr2C3, M23C6, M3C type carbides as well as a large number of dislocations and stacking fault in the austenite grains. FeS forms form on the surface of cladding Ni-based coating by ion sulfurizing treatment. Microhardness of Ni-based cladding coating reaches to 600HV(0.1) resulting from the combined effects of ultrafine dendrites and solid solution strengthening and dislocations strengthening, whereas microhardness of the composite layer decrease slightly near the surface (about 470HV(0.1)). Due to the existance of FeS film both the wear mass loss and friction coefficient of the composite layers decrease dramaticlly. Moreover, there is a slight scratch on the worn surface of laser cladding-ion sulfurizing composite layer, while worn mechanism of medium carbon steel is serious abrasion along with long and deep grooves and fatigue wear occurs on the surface of Ni-based cladding coating.